In recent years, the number of patients suffering from respiratory system diseases such as asthma, pulmonary emphysema, chronic bronchitis and the like has tended to increase. One of the most effective therapeutic methods for these diseases is oxygen inhalation therapy. In such oxygen inhalation therapy, oxygen gas or oxygen-enriched gas is inhaled by patients. An oxygen concentration device, liquid oxygen or oxygen gas cylinder, and the like are known as an oxygen supply source used for the oxygen inhalation therapy. However, an oxygen concentration device is mainly used in home oxygen therapy because it is convenient to use and easy for maintenance and management.
An oxygen concentration device is a device to supply oxygen to a user by separating and concentrating oxygen that makes up 21% of the air. As such device, there are a membrane-type oxygen concentration device that uses a membrane which selectively permeate oxygen and a pressure swing adsorption-type oxygen concentration device that uses an adsorbent which can preferentially adsorbs nitrogen or oxygen. A pressure swing adsorption-type oxygen concentration device is mainly used because it can obtain highly concentrated oxygen of 90% or more.
The pressure swing adsorption-type oxygen concentration device continuously produces a highly concentrated oxygen gas by repeating alternately an adsorption step and a desorption step. In the former step, un-adsorbed and concentrated oxygen gas is obtained by supplying air compressed by a compressor to a plurality of adsorption cylinders filled with an adsorbent, such as 5A, 13X, or Li—X type molecular sieve zeolites, which selectively adsorbs nitrogen relative to oxygen and by adsorbing nitrogen under pressurized conditions. In the latter step, the adsorbent is regenerated by desorbing and purging nitrogen adsorbed on the adsorbent under a reduced pressure of atmospheric pressure or less in the adsorption cylinder. Production of further concentrated oxygen gas is realized by, in addition to the steps of absorption and desorption, using a purge step for introducing highly concentrated oxygen from the adsorption cylinder in the adsorption step into the adsorption cylinder in the desorption step and a pressure equalization step for recovering compression energy by communicating an adsorbent cylinder that has completed the adsorption step and an adsorbent cylinder that has completed the desorption step, thereby equalizing the pressure of the two cylinders.
A pressure swing adsorption-type oxygen concentration device can produce a highly concentrated oxygen gas by being equipped with a plurality of adsorption cylinders packed with an adsorbent that selectively adsorbs nitrogen rather than oxygen, a compressor that supplies compressed air to the adsorption cylinders, a flow path switching means that repeats, by sequentially switching a flow path between the compressor and each adsorption cylinder, at a prescribed timing, an adsorption step in which pressurized air is supplied to each adsorption cylinder and concentrated oxygen is taken out, a desorption step in which each adsorption cylinder is decompressed and the adsorbent is regenerated, a pressure equalization step for communicating each of the adsorption cylinders, and a purge step where the highly oxygen-concentrated gas from an adsorption cylinder at an adsorption step side is introduced to an adsorption cylinder at a desorption step side.